(Apologies for lateness in reply: work has intervened!) On Sun, 18 Feb 2001, Mariano Alvarez Fernandez wrote: )By example in 16 color you have 16 index to colors. If you perform 1 XOR 2 you )obtain index color 3. Now, if you don't have assigned the index color 3 what )color is it?. Te answer is "undefined". A-ha. So as long as I define 2^n colours, everything behaves as expected? Does undefined refer to weird library behaviour, or is there a default behaviour for undefined colours? I don't expect this to be a problem, as I will probably just use EGA emulation for the time being: I just ask for information :) J-P -- 1. Behold the wisdom of MARKET: it is duty of us to serve MARKET, and to buy, and to fight UNION, and it is the duty of the tribes to serve the Number Beast and to serve the Others, the Shareholders.